1. Field of the Invention
This invention relates to an optical head employed in an optical information recording/reproducing apparatus such as an optical disk player, and more particularly, to an improvement in a device for supporting an object lens.
2. Description of the Prior Art
FIG. 1 is a longitudinal sectional view of an optical head disclosed in the Japanese Patent Laying-Open No. 283430/1987, and FIG. 2 is an exploded perspective view of the optical head shown in FIG. 1. Referring to these figures, a yoke member 112 formed from a sheet material is attached to a base 111. A link member 113 cast in a mold is attached via pins 114 to the yoke member 112.
A holding member 117 holding an object lens 115 and a semiconductor device 116 is attached to the forward end of the link member 113. A lid 118 having an opening 118a is attached to the holding member 117. A mirror 121 is attached to the lid 118 for closing the opening 118a. The semiconductor device 116 includes a semiconductor laser for emitting a laser beam 143 and a photosensor for sensing the laser beam reflected from a disk 144.
The link member 113 includes hinges 113a for swinging the holding member 117 along the direction of the optical axis of the object lens 115, as indicated by chain dotted lines in FIG. 1, for effecting focusing adjustment, and also includes a hinge 113b for swinging the holding member 117 along the direction normal to the optical axis of the object lens 115, for effecting tracking adjustment. Also, a counterbalance 122 is balanced against to the holding member 117 at a portion opposite to the object lens 115 with respect to the hinge 113b, for preventing the holding member 117 from being turned about the hinge 113b when the optical head is tilted in its entirety.
The yoke member 112 is provided with upstanding plate sections 112a, 112b, formed by bending. A magnet 123 is mounted to a surface of the upstanding plate section 112a confronting to the upstanding plate section 112b. A focusing coil 124 is attached to the holding member 117 for surrounding the upstanding plate section 112b. A tracking coil 125 is attached to the focusing coil 124 for confronting to the magnet 123.
Two sets each of the upstanding plate sections 112a, 112b, magnet 123, focusing coil 124 and tracking coil 125 are arranged symmetrically to each other with respect to the hinge member 113.
The semiconductor device 116, focusing coil 124 and the tracking coil 125 are connected electrically to the outside through a flexible wiring board or substrate 126.
The hinge member 113 and the holding member 117 are covered by a cap 127 having an opening 127a at a position above the object lens 115.
In the above described conventional supporting device for supporting the object lens of the optical head, the link member 113, hinge 113b and object lens 115 are arrayed along a straight line in sequence without overlapping. Hence, the object lens supporting device has a longer length, resulting in a larger size of the overall optical head.
Also, the counterbalance 122 must be inserted in the link mechanism to complete the object lens supporting device, after formation of the link mechanism including the link member 113 and the hinge 113a, thus complicating the manufacture process for the object lens supporting device.